Step 2: put the spring and detent pin into the housing. Use your brake or thread protector to hold it in place. You want the flat part lined up with the hole in the rear so you can see daylight cleanly through the smaller rear hole- this is where your roll pin will go to retain it.

Step 3: Get your roll pin punch, and hammer in the roll pin at the rear hole. You do have a roll pin punch set, right? They sure make life easy.

And BAM, it's done.

If you took the time to carefully remove the thread protector and file a retaining notch into it (chain saw sharpening file works nicely), it will work and look great when you don't want a brake.